This article examines the ability of the "Panic Attack-PTSD Model" to predict how panic attacks are generated and how panic attacks worsen posttraumatic stress disorder (PTSD). The article does so by determining the validity of the Panic Attack-PTSD Model in respect to one type of panic attacks among traumatized Cambodian refugees: orthostatic panic (OP) attacks, that is, panic attacks generated by moving from lying or sitting to standing. Among Cambodian refugees attending a psychiatric clinic, we conducted two studies to explore the validity of the Panic Attack-PTSD Model as applied to OP patients, meaning patients with at least one episode of OP in the previous month. In Study 1, the "Panic Attack-PTSD Model" accurately indicated how OP is seemingly generated: among OP patients (N = 58), orthostasis-associated flashbacks and catastrophic cognitions predicted OP severity beyond a measure of anxious-depressive distress (SCL subscales), and OP severity significantly mediated the effect of anxious-depressive distress on CAPS severity. In Study 2, as predicted by the Panic Attack-PTSD Model, OP had a mediational role in respect to the effect of treatment on PTSD severity: among Cambodian refugees with PTSD and comorbid OP who participated in a CBT study (N = 56), improvement in PTSD severity was partially mediated by improvement in OP severity.